How long have schools been having proms?

When I was at school (when guns were toys and made of plastic) we had an end of term disco. We wore the latest trend if we could afford it. In my last disco the trend was those skin tight satin trousers with a long t shirt tied in a knot at the side. Today apparently you need a limo, ball gown and diamonds. What happens to the poor kids who cant afford these luxuries? Ive just loaned my God daughter my Monsoon taffeta ball gown.